Today’s optometrists diagnose and treat a growing number of patients with ocular manifestations of systemic disease. With increasing demands for medical eyecare, optometrists must have a strong knowledge base on the plethora of systemic diseases and possible associated ocular sequelae.
In this article, we’ll review what cystic fibrosis is and how it can impact the ocular and systemic health of our patients. We’ll look at common ocular findings these patients may present with, as well as treatment and management options optometrists can use to provide quality patient care.
What is cystic fibrosis?
Cystic fibrosis (CF) is an autosomal recessive genetic disorder that primarily affects the lungs.1 It can also impact other organs, including the pancreas, liver, and intestine. It is the most common and severe genetic multisystem disease among Caucasian populations; however, it can affect individuals of any race or ethnicity. There are approximately 40,000 people currently living with CF in the United States.2
In CF, an abnormal function of sodium/chloride channels across epithelial surfaces leads to thick, viscous secretions in the gastrointestinal (GI) and respiratory tracts. This is caused by dysfunction in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. When the CFTR protein is not functioning properly or is absent altogether, chloride and water are unable to properly move in and out of the cell.
Systemic manifestations of cystic fibrosis
When the lungs are severely affected, episodes of acute and chronic hypoxia can cause chronic obstructive pulmonary disease (COPD), polyneuropathy, and affect ocular tissues, such as hypoxic damage to retinal ganglion cells. The mucus accumulation in the lungs can also clog airways and trap bacteria, leading to recurrent infections and inflammation.
In the pancreas, this abnormal accumulation of mucus prevents the proper release of digestive enzymes, leading to nutrient malabsorption and deficiencies in essential vitamins and minerals. In the liver, the mucus can cause blockage to the bile duct and subsequent liver disease.
Unfortunately, patients with CF have a high rate of morbidity and mortality due to its impact on the pulmonary system and GI tract. Those born between 2018 and 2022 with CF have an average life expectancy of approximately 56 years of age.3 This is significantly longer than it was just several decades ago.
Symptoms, diagnosis, and treatment of CF
Symptoms of CF can include persistent coughing or wheezing, frequent lung infections (e.g., pneumonia/bronchitis), abnormal growth/weight gain, rectal prolapse, and male infertility. Over 75% of people with CF are diagnosed before 2 years of age.2
Diagnosis is a multistep procedure that includes newborn screening (via blood test), sweat testing, and genetic testing. Sweat testing measures the amount of chloride present in a patient’s sweat. An abnormally high amount of chloride is typical in patients with CF. Clinical evaluation also plays a crucial role in diagnosing CF. Individuals living with CF face significant challenges, including frequent hospitalization and increased rates of diabetes, colorectal cancer, and depression.2
Treatment options for CF typically include inhaled bronchodilators and mucus thinners. Multivitamins and pancreatic enzyme supplements may also be necessary to avoid nutrient malabsorption and aid in proper digestion. Oral, inhaled, and/or intravenous antibiotics are necessary when pulmonary bacterial infections occur. In severe cases of CF, a lung transplant may also be warranted.
There are over 1,700 gene mutations associated with CF.2 Some individuals with specific gene mutations are able to take CFTR modulators as part of their treatment regime.2
Ocular manifestations of cystic fibrosis
Eyecare providers must be aware of the myriad ocular side effects that can occur in patients with CF. Unfortunately, every part of the eye is susceptible and can be affected. Patients with CF can have nutrient malabsorption, impaired storage, and subsequent deficiencies in vitamin A.4,5 Over 85% of patients with CF have shown evidence of nutrient malabsorption from a deficiency in pancreatic function.
This can lead to poor night vision (nyctalopia) as well as abnormal inflammation and dryness of the ocular surface (xerophthalmia). Both of these conditions are the ocular manifestations of CF that are most commonly seen clinically.5
Utilizing the gamut of dry eye treatment options can be an easy and effective way to build rapport and care for these patients. Depending on their signs and symptoms, these patients may need to be followed on a monthly basis initially.
While a specific CF-related dry eye treatment algorithm does not exist, these patients can be managed with aggressive ocular lubrication (e.g., preservative-free tears), topical steroids, or even scleral contact lenses in severe cases.
Ocular sequelae of cystic fibrosis
It is hypothesized that prolonged periods of vascular dysregulation and hypoxia in CF can inhibit ocular perfusion to the inner retinal tissues. CF-related diabetes (CFRD) can result in retinopathy. Approximately half of all patients with CF over 35 years of age will develop CFRD.6 It has been shown that about 50% of patients with CFRD will develop retinopathy.7
CF-related retinal vascular occlusions can also occur.5 Dilated retinal evaluations are crucial when examining these patients.4 It remains unclear whether or not CF-related retinopathy can progress faster than typical cases of diabetic retinopathy. Retinal ganglion cell loss and optic neuropathy can also occur in CF, very similar to open-angle glaucoma.1 This pathophysiology is multifactorial. CF-related optic neuropathy is likely due to hypoxia and nutrient deficiencies (e.g., vitamin B12 deficiency).8
It has been shown that inferior quadrant retinal nerve fiber layer (RNFL) thickness is most susceptible to damage in CF.9 It is unclear whether or not CF-related optic neuropathy can progress faster than typical cases of primary open-angle glaucoma. A formal glaucoma work-up with visual field testing should be performed in cases where optic nerve pathology is suspected.
Ocular sequelae of CF treatments
It has also been shown that certain medications used to treat CF may have ocular side effects, including cataracts and corneal opacities.10 These findings are thought to be caused more directly by the medication and not CF itself. The formation of cortical and subcapsular cataracts was found when initiating CF treatment with Ivacaftor (a CFTR modulator) after 84 and 96 weeks, respectively.
While other co-morbidities may also play a role in cataract formation, eyecare providers should still monitor their CF patients on CFTR modulators closely for cataracts and other vision-threatening complications. Cataract surgery may be warranted earlier in these patients. It remains unclear whether or not CF-related cataracts can progress faster than typical age-related cataracts.
Conclusion
With optometrists continuing to provide more medically-based eyecare, it’s crucial for them to understand the myriad types of systemic diseases that may present to their offices. Cystic fibrosis is one of many systemic conditions patients may present with to their optometrist. It is important for ODs to understand the nature of the condition, as well as the ocular sequelae that may occur from it (and its treatment).
To provide quality patient care, optometrists must utilize the full gamut of clinical tools and testing available to them. Co-management with pulmonology and other medical specialists is also necessary. It is important to convey all eye exam findings to the patient as well as any key medical providers involved in their care.
While less common than other systemic conditions, optometrists must be ready to provide quality, medically-based eyecare to their patients with CF. Building a doctor-patient relationship with these patients (and their families) is a great way to establish rapport and meet their eyecare needs, while also growing a practice.
